The invention resides in a crankcase of an internal combustion engine comprising a lower part and an upper part including a cylinder block having at least one cylinder, the upper and lower parts being separated along a plane extending through the center of the crankshaft bearings supported by the crankcase.
In a known crankcase of this type as shown in DE 3028788C, the side walls of the upper part and of the lower part of the crankcase are provided with weight-reducing openings which are closed on each side by various covers which are mounted onto the respective sides by screws. Since during engine operation the covers are subjected to the pressure effective in the crankcase, the covers have to be mounted by a plurality of screws in order to provide for a reliable seal. Since the effectiveness of the seal depends, among others, on the amount of torque used to tighten the screws, great care has to be taken when the covers are mounted. But even so, a sufficient engagement pressure is not insured permanently since the screws may become loose over time.
It is the object of the present invention to provide a crankcase, which is also relatively light because of openings formed in the wall which openings however are closed in a more simple and more reliable manner than it is done in the prior art arrangement.